Electrical Runaway in AlGaN/GaN HEMTs: Physical Mechanisms and Impact on Reliability

This paper deals with the deep characterization of a novel electrical parasitic effect in AlGaN/GaN technology so called “electrical runaway mechanism.” It is characterized by an anomalous gate current behaviour. Electrical measurements versus temperature show that the runaway mechanism threshold is temperature independent on the contrary to the gate current progression as a function of VDS. Optoelectrical measurements show that the physical mechanism inducing the runaway mechanism occurs below the gate area. Then, reliability aging tests performed in the frame of a 0.5-μm GaN technology present the runaway mechanism as a wear out mechanism. Finally, the runaway mechanism has been associated with tunnel conduction through gate metal and AlGaN layer.